The present invention relates to intravascular prostheses and methods of percutaneous mitral annuloplasty while monitoring hemodynamic functions such as mitral valve regurgitation.
Dilated cardiomyopathy occurs as a consequence of many different disease processes that impair myocardial function, such as coronary artery disease and hypertension. The left ventricle enlarges and the ejection fraction is reduced. The resulting increase in pulmonary venous pressure and reduction in cardiac output cause congestive heart failure. Enlargement of the mitral annulus and left ventricular cavity produce mitral valvular insufficiency. This in turn, causes volume overload that exacerbates the myopathy, leading to a vicious cycle of progressive enlargement and worsening mitral regurgitation.
According to recent estimates, more than 79,000 patients are diagnosed with aortic and mitral valve disease in U.S. hospitals each year. More than 49,000 mitral valve or aortic valve replacement procedures are performed annually in the U.S., along with a significant number of heart valve repair procedures.
Various surgical techniques have been developed to repair a diseased or damaged valve. One repair technique which has been shown to be effective in treating incompetence, particularly of the mitral and tricuspid valves, is annuloplasty, in which the effective size of the valve annulus is contracted by attaching a prosthetic annuloplasty ring to the endocardial surface of the heart around the valve annulus. The annuloplasty ring comprises an inner substrate of a metal such as stainless steel or titanium, or a flexible material such as silicone rubber or Dacron cordage, covered with a biocompatible fabric or cloth to allow the ring to be sutured to the heart tissue. The annuloplasty ring may be stiff or flexible, may be split or continuous, and may have a variety of shapes, including circular, D-shaped, C-shaped, or kidney-shaped. Examples are seen in U.S. Pat. Nos. 4,917,698, 5,061,277, 5,290,300, 5,350,420, 5,104,407, 5,064,431, 5,201,880, and 5,041,130, which are incorporated herein by reference.
Annuloplasty rings may also be utilized in combination with other repair techniques such as resection, in which a portion of a valve leaflet is excised, the remaining portions of the leaflet are sewn back together, and a prosthetic annuloplasty ring is then attached to the valve annulus to maintain the contracted size of the valve. Other valve repair techniques in current use include commissurotomy (cutting the valve commissures to separate fused valve leaflets), shortening mitral or tricuspid valve chordae tendonae, reattachment of severed mitral or tricuspid valve chordae tendonae or papillary muscle tissue, and decalcification of the valve leaflets or annulus. Annuloplasty rings may be used in conjunction with any repair procedures where contracting or stabilizing the valve annulus might be desirable.
Although mitral valve repair and replacement can successfully treat many patients with mitral valvular insufficiency, techniques currently in use are attended by significant morbidity and mortality. Most valve repair and replacement procedures require a thoracotomy, usually in the form of a median sternotomy, to gain access into the patient""s thoracic cavity. A saw or other cutting instrument is used to cut the sternum longitudinally, allowing the two opposing halves of the anterior or ventral portion of the rib cage to be spread apart. A large opening into the thoracic cavity is thus created, through which the surgical team may directly visualize and operate upon the heart and other thoracic contents. Alternatively, a thoracotomy may be performed on a lateral side of the chest, wherein a large incision is made generally parallel to the ribs, and the ribs are spread apart and/or removed in the region of the incision to create a large enough opening to facilitate the surgery.
Surgical intervention within the heart generally requires isolation of the heart and coronary blood vessels from the remainder of the arterial system, and arrest of cardiac function. Usually, the heart is isolated from the arterial system by introducing an external aortic cross-clamp through a sternotomy and applying it to the aorta to occlude the aortic lumen between the brachiocephalic artery and the coronary ostia. Cardioplegic fluid is then injected into the coronary arteries, either directly into the coronary ostia or through a puncture in the ascending aorta, to arrest cardiac function. The patient is placed on extracorporeal cardiopulmonary bypass to maintain peripheral circulation of oxygenated blood.
Of particular interest in the present application are techniques for the repair and replacement of the mitral valve. The mitral valve, located between the left atrium and left ventricle of the heart, is most easily reached through the wall of the left atrium, which normally resides on the posterior side of the heart, opposite the side of the heart that is exposed by a median sternotomy. Therefore, to access the mitral valve via a sternotomy, the heart is rotated to bring the left atrium into an anterior position. An opening, or atriotomy, is then made in the right side of the left atrium, anterior to the right pulmonary veins. The atriotomy is retracted by means of sutures or a retraction device, exposing the mitral valve adjacent to the atriotomy. One of the previously identified techniques may then be used to repair or replace the valve.
An alternative technique for mitral valve access has been used when a median sternotomy and/or rotational manipulation of the heart are inappropriate. In this technique, a thoracotomy is made in the right lateral side of the chest, usually in the region of the fourth or fifth intercostal space. One or more ribs may be removed from the patient, and other ribs near the incision are retracted outward to create a large opening into the thoracic cavity. The left atrium is then exposed on the posterior side of the heart, and an atriotomy is formed in the wall of the left atrium, through which the mitral valve may be accessed for repair or replacement.
Using such open-chest techniques, the large opening provided by a median sternotomy or right thoracotomy enables the surgeon to see the mitral valve directly through the left atriotomy, and to position his or her hands within the thoracic cavity in close proximity to the exterior of the heart for cannulation of the aorta and/or coronary arteries to induce cardioplegia, manipulation of surgical instruments, removal of excised tissue, and introduction of an annuloplasty ring or a replacement valve through the atriotomy for attachment within the heart.
Mitral valve surgery, including mitral annuloplasty, is usually applied to patients with intrinsic disease of the mitral apparatus. As described above, these patients may have scarring, retraction, tears or fusion of valve leaflets as well as disorders of the subvalvular apparatus. Definitive repair requires direct visualization of the valve.
Patients who develop mitral regurgitation as a result of dilated cardiomyopathy do not have intrinsic mitral valve disease. Regurgitation occurs as the result of the leaflets being moved back from each other by the dilated annulus. The ventricle enlarges and becomes spherical, pulling the papillary muscles and chordae away from the plane of the valve and further enlarging the regurgitant orifice. In these patients, correction of the regurgitation does not require repair of the valve leaflets themselves, but simply a reduction in the size of the annulus and the sphericity of the left ventricle.
Mitral annuloplasty without repair of the leaflets or chordae has been shown to be effective in patients with dilated cardiomyopathy who are refractory to conventional medical therapy. Bolling and coworkers have operated on a cohort of such patients with New York Heart Association Class III and IV symptoms. Average symptom severity decreased from 3.9 preoperatively to 2.0 after surgery. Hemodynamics and ejection fraction improved significantly. Other investigators have achieved similar results as well. However, the morbidity, risks and expense of surgical annuloplasty are very high in patients with cardiomyopathy and congestive heart failure. Thus, a variety of new techniques for the treatment of congestive heart failure are being explored as adjuncts to drug therapy.
Several cardiac restraint devices have been described. U.S. Pat. No. 5,702,343 to Alferness discloses a cardiac reinforcement device that is applied as a jacket over the epicardium in order to limit diastolic expansion. However, this requires an open chest operation to implant and does not directly affect the diameter of the mitral annulus. Another approach is disclosed in U.S. Pat. No. 5,961,440 to Schweich, et al., in which tension members are placed through opposite walls of the heart such that they span the ventricle. Less invasive and xe2x80x9cminimallyxe2x80x9d invasive techniques for valve repair and replacement continue to evolve, both on a stopped heart and on a beating heart. These techniques may provide some benefits over open chest procedures, but they are still attended by significant morbidity and mortality risks.
A need therefore remains for methods and devices for treating mitral valvular insufficiency, which are attended by significantly lower morbidity and mortality rates than are the current techniques, and therefore would be well suited to treat patients with dilated cardiomyopathy. Optimally, the procedure can be accomplished through a percutaneous, transluminal approach, using simple, implantable devices which do not depend upon prosthetic valve leaflets or other moving parts.
There is provided in accordance with one aspect of the present invention, a method of treating a patient. The method comprises the steps of transluminally advancing a prosthesis into the coronary sinus, and manipulating the prosthesis to exert a compressive force on the mitral valve annulus. Hemodynamic function is monitored to assess mitral valve regurgitation.
The monitoring step may comprise monitoring hemodynamic function prior to the manipulation step, during the manipulation step, and/or following the manipulation step. Preferably, the method comprises the step of percutaneously accessing the venous system prior to the transluminally advancing step. The accessing step may be accomplished by accessing one of the internal jugular, sub-clavian, or femoral veins.
The manipulating step comprises bonding the prosthesis within the coronary sinus, such as by axially moving a forming element with respect to the prosthesis, to bend the prosthesis. The transluminally advancing step may be accomplished using a catheter. The method may additionally comprise the step of locking the prosthesis to retain a compressive force on the annulus following the manipulation step. The locking step may comprise moving an engagement surface from a disengaged configuration to an engaged configuration. The locking step may comprise providing an interference fit, providing an adhesive bond, providing a knot, or providing a compression fit. The coronary sinus may be measured and an appropriately sized prosthesis may be selected prior to the inserting step.
The monitoring hemodynamic function step may be accomplished using transesophageal echo cardiography, surface echo cardiographic imaging, intracardiac echo cardiographic imaging, using fluoroscopy with radio contrast media, or by using left atrial or pulmonary capillary wedge pressure measurements. The method may additionally comprise the step of determining an on-going drug therapy, taking into account post-implantation hemodynamic function.
In accordance with another aspect of the present invention, there is provided a method of remodeling a mitral valve annulus to reduce mitral valve regurgitation. The method comprises the steps of providing a prosthesis which is adjustable between a first configuration for transluminal deployment within the coronary sinus, throughout a range to a second configuration for exerting a compressive force against the mitral valve annulus from within the coronary sinus. The prosthesis is transluminally advanced to a position at least partially within the coronary sinus, and the prosthesis is tightened to reduce mitral valve regurgitation. The degree of regurgitation is monitored, prior to the tightening step, during the tightening step, and/or following the tightening step. In one application of the invention, sufficient tightening is accomplished to achieve at least a one grade reduction in regurgitation.
There is provided in accordance with a further aspect of the present invention, a method of treating mitral valvular insufficiency. The method comprises the steps of tranvenously advancing a prosthesis into the coronary sinus, and deploying at least a portion of the prosthesis within the coronary sinus to reduce the diameter of the mitral annulus. Although deployment can be accomplished in an open surgical procedure, the method preferably further comprises the step of percutaneously accessing the venous system prior to the transluminally advancing step. The venous system may be accessed by one of the internal jugular, subclavian, or femoral veins. Preferably, the deploying step further includes the step of advancing the prosthesis from a first configuration for transluminal implantation to a second configuration to apply pressure to the wall of the coronary sinus and thereby reduce and/or restrain the diameter of the mitral valve annulus.
In accordance with another aspect of the present invention, there is provided a method of performing transluminal mitral annuloplasty. The method comprises the steps of providing a catheter which carries a prosthesis, and percutaneously inserting the catheter into the venous system. The prosthesis is transluminally advanced into the coronary sinus, and deployed in the coronary sinus to influence the size of the mitral valve annulus. Preferably, the prosthesis is caused to exert a compressive force on the mitral valve annulus.
The compressive force is generated by tightening the prosthesis around the mitral valve annulus following the transluminally advancing step. The tightening step may be accomplished by axial movement of a tightening element with respect to the prosthesis.
In accordance with a further aspect of the present invention, there is provided a method of providing a therapeutic compressive force against a tissue structure which is distinct from a vessel wall. The method comprises the steps of positioning a device in the vessel, and exerting a force against the wall of the vessel to exert a force against an extravascular tissue structure. Preferably, the positioning step is accomplished percutaneously. In one application, the extravascular tissue structure comprises the mitral valve annulus. Thus, the present invention provides a method of performing annuloplasty of the mitral valve, comprising positioning a prosthesis in the venous sinus.
In accordance with another aspect of the present invention, there is provided an implant for extravascular remodeling, for positioning within a vascular structure to influence tissue outside of the vessel. The implant comprises an elongate flexible support, having a proximal end and a distal end. Each of the proximal and distal ends are dimensioned to reside completely within the vascular system. A forming element is attached to the support, such that movement of the forming element relative to the support changes the shape of the support. The support is thus moveable between an implantation configuration for transluminal implantation and a remodeling configuration for exerting a force against a vessel wall. In one application, the support defines an arc when in the remodeling configuration.
Preferably, the implant for extravascular remodeling further comprises a lock for restraining the support in the remodeling configuration. In one embodiment, the lock comprises a locking ring. Alternatively, the lock comprises a compression fit, an interference fit or an adhesive bond.
The support is moveable from the implantation configuration to the remodeling configuration in response to movement of a remodeling control such as proximal retraction of the forming element. Alternatively, the support is moveable from the implantation configuration to the remodeling configuration in response to distal advancement of the forming element.
In one embodiment, the implant for extravascular remodeling further comprises an anchor for retaining the implant at a deployment site within a vessel. In one application, the anchor comprises a distal extension of the support, for positioning within the great cardiac vein. Alternatively, the anchor comprises a friction enhancing surface texture or structure for engaging the wall of the vessel. In a further embodiment, the anchor comprises at least one barb for piercing the wall of the vessel.
In accordance with yet a further aspect of the present invention, there is provided a transluminally implantable annuloplasty device. The annuloplasty device comprises a flexible body, having a proximal end and a distal end. An annuloplasty zone is provided on a proximal portion of the body, and an anchor zone is provided on a distal portion of the body. An axially moveable forming element is attached to the body between a mid-point of the annuloplasty zone and a mid-point of the anchor zone, such that proximal retraction of the forming element with respect to the proximal end of the body advances at least the annuloplasty zone into an arcuate configuration.
In accordance with a further aspect of the present invention, there is provided a method of treating a mitral valve. The method comprises the steps of providing an elongate flexible vascular implant, having a first attachment site spaced axially apart from a second attachment site. The first attachment site is transluminally advanced through the coronary sinus and coronary venous system to form the implant into an open loop. The open loop is reduced in size to place tension on the coronary sinus, and the first attachment site is attached to the second attachment site to close the loop and retain tension on the coronary sinus.
In accordance with another aspect of the present invention, there is provided a method of treating the heart. The method comprises the steps of advancing an implant through an access site and into a coronary vein such as the coronary sinus. A forming element on the implant is thereafter proximally retracted while resisting proximal movement of the implant, thereby forming the implant into a desired shape. The access site is thereafter closed, leaving the formed implant within the coronary vein.
Preferably, the method further comprises the step of locking the implant into the desired shape prior to the closing step. The method may additionally comprise the step of severing at least a portion of the forming element prior to the closing step.
Further features and advantages of the present invention will become apparent to those of ordinary skill in the art in view of the detailed description of preferred embodiments which follows, when considered together with the attached drawings and claims.